x86, efi: Merge contiguous memory regions of the same type and attribute

Some firmware implementations assume that physically contiguous regionswill be contiguous in virtual address space. This assumption is, obviously,entirely unjustifiable. Said firmware implementations lack the good graceto handle their failings in a measured and reasonable manner, insteadtending to shit all over address space and oopsing the kernel.

In an ideal universe these firmware implementations would simultaneouslycatch fire and cease to be a problem, but since some of them are presentin attractively thin and shiny metal devices vanity wins out and somepoor developer spends an extended period of time surrounded by agrowing array of empty bottles until the underlying reason becomesapparent. Said developer presents this patch, which simply mergesadjacent regions if they happen to be contiguous and have the same EFImemory type and caching attributes.